Eucalyptus polybractea

Eucalyptus polybractea, commonly known as the blue-leaved mallee or simply blue mallee,[2] is a species of mallee that is endemic to south-eastern Australia. It has rough, fibrous or flaky bark on the lower part of the trunk, smooth greyish or brownish bark above, lance-shaped adult leaves, flower buds in groups of between seven and eleven, white flowers and cup-shaped or barrel-shaped fruit.

Blue-leaved mallee
Eucalyptus polybractea near West Wyalong
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Myrtales
Family: Myrtaceae
Genus: Eucalyptus
Species:
E. polybractea
Binomial name
Eucalyptus polybractea
flower buds and flowers
leaves

Description

Eucalyptus polybractea is a mallee that typically grows to a height of 8–10 m (26–33 ft) and forms a lignotuber. It has rough, fibrous or flaky, greyish to brownish bark on the lower part of the trunk, smooth greyish to brownish bark above that is shed in ribbons. Young plants and coppice regrowth have bluish to glaucous, linear to lance-shaped leaves that are 40–150 mm (1.6–5.9 in) long and 3–16 mm (0.12–0.63 in) wide. Adult leaves are the same shade of bluish green on both sides, lance-shaped, 60–170 mm (2.4–6.7 in) long and 4–20 mm (0.16–0.79 in) wide, tapering to a petiole 4–15 mm (0.16–0.59 in) long. The flower buds are arranged in leaf axils in groups of seven, nine or eleven on an unbranched peduncle 4–12 mm (0.16–0.47 in) long, the individual buds on pedicels up to 4 mm (0.16 in) long. Mature buds are club-shaped to diamond-shaped, 4–6 mm (0.16–0.24 in) long and 3–4 mm (0.12–0.16 in) wide with a conical to rounded operculum. Flowering mainly occurs from March to August and the flowers are white. The fruit is a woody, cup-shaped or barrel-shaped capsule 4–7 mm (0.16–0.28 in) long and 3–5 mm (0.12–0.20 in) wide with the valves near rim level.[2][3][4][5]

Taxonomy and naming

Eucalyptus polybractea was first formally described in 1901 by Richard Thomas Baker in Proceedings of the Linnean Society of New South Wales from specimens collected near West Wyalong by Richard Hind Cambage.[6][7] The specific epithet (polybractea) is from the ancient Greek poly- and the Latin bractea, referring to the many bracts of this species, although many eucalytps have "many bracts" at the base of immature flowers.[2]

In 2018, Kevin James Rule described two subspecies, polybractea and suberea but the names have not been accepted by the Australian Plant Census.[8]

Distribution

Blue-leaved mallee has a wide, but sporadic distribution around West Wyalong in New South Wales and between Stawell and Bendigo in Victoria. In grows in mallee shrubland on loamy soils.[2][4]

Uses

Essential oil

Eucalyptus polybractea leaves are used to produce eucalyptus oil with very high levels of cineole (up to 91%), yielding 0.7-5% fresh weight overall. The oil is primarily used medicinally and for flavoring.[9]

Carbon sequestration

This eucalypt is the most commonly planted tree in Australia as part of carbon offset programs. Primarily, this is because the blue-leaved mallee is native to Australia, can grow effectively in drought conditions and can store a great deal of carbon quickly.[10]

See also

References
  1. "Eucalyptus polybractea". Australian Plant Census. Retrieved 4 December 2019.
  2. "Eucalyptus polybractea". Euclid: Centre for Australian National Biodiversity Research. Retrieved 30 May 2020.
  3. Brooker, M. Ian H.; Slee, Andrew V. "Eucalyptus polybractea". Royal Botanic Gardens, Victoria. Retrieved 4 December 2019.
  4. Hill, Ken. "Eucalyptus polybractea". Royal Botanic Garden Sydney. Retrieved 4 December 2019.
  5. Chippendale, George M. "Eucalyptus polybractea". Australian Biological Resources Study, Department of the Environment and Energy, Canberra. Retrieved 4 December 2019.
  6. "Eucalyptus polybractea". APNI. Retrieved 4 December 2019.
  7. Baker, Richard Thomas (1901). "On some new species of Eucalyptus". Proceedings of the Linnean Society of New South Wales. 25 (4): 692–695. doi:10.5962/bhl.part.12184. Retrieved 4 December 2019.
  8. Rule, Keven J. (2018). "Eucalyptus wimmerensis revisited and notes on the morphologies and taxonomies of five Victorian mallee-boxes" (PDF). Muelleria. 37: 55–58. Retrieved 4 December 2019.
  9. Boland, Douglas J. (ed.); Brophy, Joseph J.; Pennock, Alan (1991). Eucalyptus Leaf Oils: Use, Chemistry, Distillation and Marketing. Inkata Press. ISBN 0909605696.CS1 maint: extra text: authors list (link)
  10. "How Much Carbon Does A Tree Offset & Which Tree is Best?". CO2 Australia. 4 December 2013. Retrieved 10 June 2019.
  • Harden, G.J., Flora of New South Wales, Volume 2, ISBN 0-86840-164-1.
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